Recently, digital cameras are rapidly pluralized. Generally, the digital cameras have a display unit such as a liquid crystal display to reproduce a video image being image-sensed or already recorded in a storage medium such as a memory card, and an image which has been obtained can be checked on the spot of image sensing. This is one of the factors of the popularity. In addition, obtained images can be deleted in accordance with necessity. Further, the number of image sensing pixels has been increased to several millions to attain image quality equivalent to that obtained by a silver-salt camera. These facts may other factors of the popularity.
As described above, in many digital cameras, it is possible to display images stored in a storage medium (generally JPEG coded) on a display unit one by one. Further, some digital cameras have an attitude sensor such that the attitude upon image sensing, i.e., information on portrait image sensing or landscape image sensing is stored. Upon display of obtained image, the decoded image data is rotated in accordance with the information, and an image in an erect position is displayed on the display unit.
As the display unit, the liquid crystal display has a display capability of at most 640×480 dots which is far less than the resolution of images stored in the storage medium. Accordingly, processing upon display of stored image on the display unit includes reading a JPEG file from the storage medium, decoding, and thinning, to attain the 640×480 dot display resolution.
During the image display, it is also possible to enlarge a desired part of the display image (e.g., Japanese Patent Application Laid-Open No. 10-336494). Further, known is a technique of storing images in two different resolutions and displaying a low resolution image for checking, thereby improving the response to frame advance (Japanese Patent Application Laid-Open Nos. 2003-087715 and 2003-087716).
Assume that a digital camera has a frame advance function of sequentially displaying images, a function of enlarging an image part, and an image rotating function. That is, in this case, a user's requests include at least a frame advance (reverse) request, an enlargement request, and a rotation request.
According to Japanese Patent Application Laid-Open Nos. 2003-087715 and 2003-087716, as two images in different resolutions are stored and a low resolution image is displayed for checking, a high response can be expected in frame advance, however, the amount of consumption of recording medium is increased and then inevitably the number of storable images is limited. Further, in this art, image enlargement and rotation with enlargement cannot be handled.
Further, as the number of pixels of low resolution images is far smaller than the number of pixels of the liquid crystal display, to produce a display in correspondence with the resolution of the liquid crystal display, enlargement processing must be performed. As a result, the user checks merely a rough image.
Further, to effectively utilize the resolution of the liquid crystal display, an original image in a high resolution may be processed and displayed. In this case, if the rotation request has been made in correspondence with the image sensing attitude, as the original image must be rotate-processed, it takes time to display a rotated image.